Copending application Ser. No. 11/726,391 filed Mar. 21, 2007, of common assignee discloses a haptic device having a tactile interface based on modulating the surface friction of a substrate, such as glass plate, using ultrasonic vibrations. The device can provide indirect haptic feedback and virtual texture sensations to a user by modulation of the surface friction in response to one or more sensed parameters and/or in response to time (i.e. independent of finger position). A user actively exploring the surface of the device can experience the haptic illusion of textures and surface features.
This haptic device is resistive in that it can only vary the forces resisting finger motion on the interface surface, but it cannot, for instance, re-direct finger motion.
It would be desirable to provide the variable friction benefits of this haptic device and also to provide shear forces to a user's finger or an object on the interface surface of the glass plate substrate.